1. Technical Field
This invention pertains to a method and device for removing condensation from eyeglasses.
2. Background Art
Eyeglasses used out-of-doors in cold climates are subject to fogging due to the accumulation of water vapor on the lenses. Such condensation hinders the user's ability to see through the lenses, whether the lenses are optically corrective or simply to protect the user's eyes from bright sunlight.
The use of electrical heating to prevent or remove condensation on lenses or face masks is known in the prior art. For example, U.S. Pat. No. 4,209,234 to McCooeye discloses a pair of eyeglasses in which a battery is mounted on the temples of the glasses to supply power to an electrical circuit which includes a conductive transparent film covering the lenses of the eyeglasses. Great Britain Patent No. 489,530 reveals lenses which are coated with a conductive metal paint, and which are superimposed on a second set of lenses, embedding a wire which forms a portion of an electrical circuit for heating the lenses. U.S. Pat. No. 3,160,735 to Aufricht, like McCooeye, relies on a battery mounted in the temple of eyeglasses. This miniature battery supplies power to an electrical circuit which includes a wire around each lens. Batteries mounted on the glasses themselves increase the weight of the glasses and cause the glasses to be considerably different in appearance and in construction than standard eyeglasses. Furthermore, the use of miniature batteries, which enables these designs to be comfortably worn, results in a maximum time for supplying power of approximately one to two hours under moderate fogging conditions, and no more than ten minutes in severe fogging conditions, which is significantly less than is required to permit defogging during a day of work or sports.
A number of specialized goggles and helmets are known in the prior art, which achieve defogging based on an electrical circuit supplied from an exterior power supply such as a vehicle electrical system. See, for example, U.S. Pat. No. 4,638,728 to Elenewski, U.S. Pat. No. 4,584,721 to Yamamoto, U.S. Pat. No. 3,024,341 to Ogle Jr. et al., and U.S. Pat. No. 4,682,007 to Hollander. Use of the external vehicle power source alleviates the problems associated with using a small battery pack to defog eyewear, and allows virtually limitless time periods for heating the eyewear. These designs are useful for activities involving consistent contact with a vehicle, such as snow mobiling. However, reliance on an external vehicle power source makes it impossible to utilize these defogging systems in sports such as skiing.
Goggles which may be heated to achieve defogging are revealed in U.S. Pat. No. 4,942,629 to Stadlmann, U.S. Pat. No. 3,027,561 to Senne, Great Britain Patent No. 264,280, U.S. Pat. No. 1,963,990 to Gilkeson et al., and U.S. Pat. No. 4,868,929 to Curcio. The power source used in Stadlmann is a solar cell mounted in a headband, which provides less than optimum heating capacity on cloudy days. Senne and Great Britain 264,280 are geared toward applications other than winter weather, and each relies on wires embedded in lenses to complete an electrical circuit and heat the lenses. Similarly, a wire is embedded in aircraft and ski goggles in Gilkeson and Curcio respectively, to heat the lenses and accomplish defogging.
Other eyewear or helmets with mechanisms for clearing condensation are known in the prior art. U.S. Pat. No. 4,996,981 to Elenewski et al. describes a visor to be used by a fireman or miner with an electrically activated heater or fan to prevent condensation from forming on the visor. U.S. Pat. No. 4,633,532 to Yagasaki and U.S. Pat. No. 2,888,703 to Karwowska both involve the use of miniature "windshield wipers" to remove condensation. Finally, U.S. Pat. No. 1,488,085 to Zachara discloses an electrically powered eye glass frame which is intended to be used as a light source.
While each of these mechanisms known in the prior art may be useful for its intended purpose, no mechanism is known which may be used to defog eyeglasses for a period as long as a day during use in winter weather, while achieving a customary construction, appearance, and weight for the eyeglasses. There exists a need for a defogging mechanism which can be used for a period of at least six hours during outdoor winter work or sports activities, while maintaining the comfort and typical appearance of eyeglasses. Ideally, such a defogging mechanism should permit the eyeglasses to be manufactured by existing production techniques, to avoid additional expense. Furthermore, this defogging means should utilize a convenient, portable, and economical power source.